Users can now leverage iOS' geofencing to tell OmniFocus to sync its online database in the background and automatically whenever they enter or leave a specific location. There's a new Background Sync screen in the settings where locations can be configured, which works similarly to Instapaper's one. Unlike CameraSync, I wasn't able to receive a local notification when I left or arrived at a location that triggered background sync.

The Omni Group is undoubtedly looking at iOS 7's new background app refresh options, but, until then, this is a nice (and common) workaround.